You have been very close to the answer. You should just add an asterisk as a very first character in the exclude
pattern. Taking your sample, this will loot like this:
<target name="createArtifacts">
<copy todir="${destdir}" includeemptydirs="false">
<fileset basedir="${sourcedir}">
<include name="**" />
<exclude name="*\**\bin\*.pdb" />
<exclude name="*\**\bin\*.xml" />
...
</fileset>
</copy>
</target>
That first asterisk basically means "we don't want to take first-level folder into consideration".